Multi-joint implant

ABSTRACT

Methods and devices are provided for repairing or replacing damaged, injured, diseased, or otherwise unhealthy posterior elements, such as the facet joints, the lamina, the posterior ligaments, and/or other features of a patient&#39;s spinal column. In one exemplary embodiment, an implant is provided having an anterior portion that is adapted to be positioned between adjacent vertebrae and a posterior portion that is adapted to be positioned around a spinal cord and to couple to a posterior surface of at least one adjacent vertebra. In use, the implant can allow the adjacent vertebrae to move relative to one another, thereby restoring normal function to the vertebrae.

CROSS REFERENCE TO RELATED APPLICATIONS

The present invention claims priority to U.S. Provisional ApplicationSer. No. 60/584,022, filed on Jun. 30, 2004 and entitled “Multi-Joint(Disc & Facet) Implant,” which is hereby incorporated by reference inits entirety.

FIELD OF THE INVENTION

The present invention relates to spinal implants and methods.

BACKGROUND OF THE INVENTION

The vertebrae in a patient's spinal column are linked to one another bythe disc and the facet joints, which control movement of the vertebrae.Each vertebra has a pair of articulating surfaces located on the leftside, and a pair of articulating surfaces located on the right side, andeach pair includes a superior articular surface, which faces upward, andan inferior articular surface, which faces downward. Together thesuperior and inferior articular surfaces of adjacent vertebra form afacet joint. Facet joints are synovial joints, which means that eachjoint is surrounded by a capsule of connective tissue and produces afluid to nourish and lubricate the joint. The joint surfaces are coatedwith cartilage allowing the joints to move or articulate relative to oneanother. In combination with the intervertebral disc, the two facetjoints form the spinal three-joint complex.

Diseased, degenerated, impaired, or otherwise painful facet jointsand/or discs can require surgery to relieve pain or restore function tothe three-joint complex. Subsequent surgery may also be required after alaminectomy, as a laminectomy predisposes the patient to instability andmay lead to post-laminectomy kyphosis (abnormal forward curvature of thespine), pain, and neurological dysfunction. Current clinical data havesuggested that degeneration of one member of the three joint complex,that is either the discs or the facet joints, contributes to thedegeneration of the other. While implants are available for replacingeither a diseased disc or the facet joints, there are no implants thatcan be used to replace the entire spinal three-joint complex.

Accordingly, there remains a need for improved systems and methods forrepairing and/or replacing the spinal three-joint complex.

BRIEF SUMMARY OF THE INVENTION

The present invention provides various methods and devices for repairingor replacing damaged, injured, diseased, or otherwise unhealthyposterior elements, such as the facet joints, the lamina, the posteriorligaments, and/or other features of a patient's spinal column. In oneexemplary embodiment, a spinal implant is provided having an anteriorportion that is adapted to be positioned between adjacent vertebrae, anda posterior portion that is adapted to be positioned around a spinalcord and to couple to at least one adjacent vertebra.

The implant can have a variety of shapes and sizes, but in one exemplaryembodiment the implant is substantially C-shaped such that the posteriorportion is curved or semi-circular with an opening formed therein andthe anterior portion includes opposed arms that extend from theposterior portion. The posterior and anterior portions of the implantcan have a variety of configurations, but in one exemplary embodimentthe anterior portion of the implant has a shape that is adapted to allowarticulation of adjacent vertebrae relative to one another, and theposterior portion of the implant includes at least one extension memberextending therefrom and adapted to mate to a posterior surface of avertebra. The extension member(s) can have a variety of configurations,and it can be rigidly or movably coupled to the implant. In oneexemplary embodiment, the extension member(s) is an elongate memberhaving at least one thru-bore formed therein for receiving a fasteningelement adapted to mate the extension member(s) to a vertebra. Theimplant can also include any number of extension members, but in oneexemplary embodiment the implant includes first and second extensionmembers extending from opposed lateral sides of the posterior portion ofthe implant. The first and second extension members can extend in asuperior direction from a superior surface of the posterior portion ofthe C-shaped member, or alternatively they can extend in an inferiordirection from an inferior surface of the posterior portion of theimplant. In another exemplary embodiment, the implant can include firstand second superior extension members extending in a superior directionfrom opposed lateral sides of the posterior portion of the implant, andfirst and second inferior extension members extending in an inferiordirection from opposed lateral sides of the posterior portion of theimplant.

In another exemplary embodiment, the implant can include a substantiallyC-shaped superior member, a substantially C-shaped inferior member, andat least one central member disposed therebetween. In certainembodiments, the implant can include first and second central membersdisposed between the anterior portion of the superior and inferiormembers, and third and fourth central members disposed between theposterior portion of the superior and inferior members. In use, thecentral member(s) can be adapted to articulate between the superior andinferior members. In other embodiments, the central member(s) can becompressible to allow movement of the superior and inferior membersrelative to one another.

The present invention also provides exemplary methods for stabilizingadjacent vertebrae. In one embodiment, the method can includepositioning a posterior portion of an implant around a spinal cord andbetween resected facets of adjacent vertebrae. The posterior portion ofthe implant can be adapted to couple to at least one of the adjacentvertebrae. The method can further include positioning an anteriorportion of the implant between the adjacent vertebrae such that theadjacent vertebrae are adapted to move relative to one another.

In another exemplary embodiment, a method for stabilizing adjacentvertebrae is provided and includes accessing a patient's spinal columnusing a posterior surgical approach, removing a disc disposed betweenadjacent vertebrae, posteriorly positioning an implant around a spinalcord, between facet joints of adjacent vertebrae, and between theadjacent vertebrae, and coupling a posterior portion of the implant toat least one of the adjacent vertebrae. In an exemplary embodiment, theposterior portion of the implant is coupled to at least one of theadjacent vertebrae by inserting at least one bone screw through at leastone extension formed on the posterior portion of the implant and intothe vertebra.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detaileddescription taken in conjunction with the accompanying drawings, inwhich:

FIG. 1A is a perspective view of one exemplary embodiment of a spinalimplant having a unitary disc replacement member with first and secondfacet replacement members movably coupled thereto;

FIG. 1B is a cross-sectional view of the spinal implant shown in FIG. 1Ataken across line B-B;

FIG. 1C is a superior perspective view of the spinal implant shown inFIG. 1A implanted between adjacent vertebrae, showing only the inferiorvertebra;

FIG. 1D is a posterior perspective view of the spinal implant shown inFIG. 1A implanted between adjacent superior and inferior vertebrae;

FIG. 2A is an anterior perspective view of another exemplary embodimentof a spinal implant having a multi-piece construction;

FIG. 2B is a superior cross-sectional view, taken in the axial plane, ofthe spinal implant shown in FIG. 2A implanted between adjacentvertebrae, showing only the inferior vertebra;

FIG. 2C is a superior perspective view of the spinal implant shown inFIG. 2A implanted between adjacent vertebrae, showing only the inferiorvertebra;

FIG. 2D is a posterior perspective view of the spinal implant shown inFIG. 2A implanted between adjacent superior and inferior vertebrae;

FIG. 3A is an anterior perspective view of yet another exemplaryembodiment of a spinal implant having a multi-piece construction withextensions members formed thereon; and

FIG. 3B is a posterior perspective view of the spinal implant shown inFIG. 3A implanted between and coupled to adjacent superior and inferiorvertebrae.

DETAILED DESCRIPTION OF THE INVENTION

Certain exemplary embodiments will now be described to provide anoverall understanding of the principles of the structure, function,manufacture, and use of the devices and methods disclosed herein. One ormore examples of these embodiments are illustrated in the accompanyingdrawings. Those of ordinary skill in the art will understand that thedevices and methods specifically described herein and illustrated in theaccompanying drawings are non-limiting exemplary embodiments and thatthe scope of the present invention is defined solely by the claims. Thefeatures illustrated or described in connection with one exemplaryembodiment may be combined with the features of other embodiments. Suchmodifications and variations are intended to be included within thescope of the present invention.

The present invention provides various methods and devices for repairingor replacing damaged, injured, diseased, or otherwise unhealthyposterior elements, such as the facet joints, the lamina, the posteriorligaments, and/or other features of a patient's spinal column. In oneexemplary embodiment, an implant is provided having an anterior portionthat is adapted to be positioned between adjacent vertebrae and aposterior portion that is adapted to be positioned around a spinal cordand to couple to at least one adjacent vertebra. In use, the implant canallow the adjacent vertebrae to move relative to one another, therebyrestoring normal function to the vertebrae.

FIGS. 1A-1B illustrate one exemplary embodiment of a spinal implant 10for replacing or repairing a damaged spinal disc, the facet joints, andoptionally other posterior elements of the spine. In general, theimplant 10 includes a posterior portion 12 a that is adapted to bepositioned around the spinal cord, and an anterior portion 12 b that isadapted to be positioned between adjacent vertebrae. The anterior andposterior portions 12 a, 12 b are collectively referred to herein as adisc replacement component 12. The implant 10 can also include a facetreplacement component 20 that is adapted to couple the disc replacementcomponent 12 to at least one adjacent vertebrae. In use, the facetreplacement component 20 can move relative to the disc replacementcomponent 12 to allow the adjacent vertebrae to move relative to oneanother, thereby restoring normal function to the vertebrae.

The disc replacement component 12 can have a variety of configurations,but in the illustrated exemplary embodiment it is substantially U-shapedor C-shaped. A person skilled in the art will appreciate that the terms“U-shaped” or “C-shaped” are intended to include any implant having agenerally or partially curved structure with an opening in one sidethereof. Further, these terms are intended to include any implant thathas an open anterior portion and a posterior portion that can bedisposed around a spinal cord, and an anterior portion that can bedisposed between adjacent vertebrae. The shape and configuration of theimplant is not intended to be limited to only a U- or C-shapedconfiguration.

The posterior portion 12 a of the disc replacement component 12 can havea variety of shapes and sizes, but in the illustrated exemplaryembodiment the posterior portion 12 a is in the form of a substantiallysemi-circular member having a relatively large central opening 17 aformed therein. Such a shape allows the posterior portion 12 a to bepositioned around the spinal cord in a patient's spinal column. Theposterior portion 12 a can also have a relatively low profile, so as toallow the posterior portion 12 a to be positioned between the spinousprocesses of adjacent vertebrae.

The anterior portion 12 b of the disc replacement component 12 can alsohave a variety of shapes and sizes, but in the illustrated exemplaryembodiment the anterior portion 12 b of the disc replacement component12 includes opposed arms 14, 16 that extend from the posterior portion12 a in a substantially parallel arrangement and that define an opening17b therebetween. The opening 17 b between the arms 14, 16 can besmaller than the opening 17 a at the posterior portion 12 a of the discreplacement component 12, but it is preferably large enough to allow thespinal cord to pass therethrough when the implant 10 is being implanted.While the shape and size of each arm 14, 16 can vary, in one exemplaryembodiment each arm 14, 16 is in the form of a lobe that extends fromthe posterior portion 12 a, and that has a height h₁, h₂ that is greaterthan a height h₃ of the posterior portion 12 a, and a width w₁, w₂ thatis greater than a width w₃ of the posterior portion 12 a of the implant10, as shown in FIGS. 1A and 1B. Such a configuration allows the arms14, 16 to occupy additional space between the adjacent vertebrae,thereby providing sufficient support for the vertebrae.

The opposed arms 14, 16 can also include a variety of other featuresthat can vary depending on the intended use and desired result onceimplanted. For example, in one exemplary embodiment each arm 14, 16 canhave a shape that is adapted to allow the adjacent vertebrae toarticulate relative thereto. For example, as shown in FIGS. 1A and 1B,each arm 14, 16 includes curved or domed superior and inferior surfaces14 s, 16 s, 14 i, 16 i. The domed surfaces 14 s, 16 s, 14 i, 16 i can beformed on any portion of each arm 14, 16, but in one exemplaryembodiment the domed surfaces 14 s, 16 s, 14 i, 16 i are formed alongthe anterior portion 12 b of the implant 10 adjacent to the terminal endof each arm 14, 16. As a result, when the arms 14, 16 are positionedbetween adjacent vertebrae, the domed surfaces 14 s, 16 s, 14 i, 16 iwill be substantially centrally located relative to the adjacentvertebrae, thereby allowing the vertebrae to articulate relativethereto. While domed surfaces 14 s, 16 s, 14 i, 16 i are shown, the arms14, 16 can have a variety of other configurations to allow articulationof adjacent vertebrae. For example, each arm 14, 16 can include a ballor other member movably disposed therein or coupled thereto.

In another exemplary embodiment, the opposed arms 14, 16 can be adaptedto engage the adjacent vertebrae. Techniques for mating the arms 14, 16to adjacent vertebrae include, by way of non-limiting example, surfacefeatures, such as teeth, that engage the endplates of the vertebrae,surface coatings or materials that allow bone growth into the implant 10to occur, or other materials or features that will engage the adjacentvertebrae.

In an exemplary embodiment, where engagement features are included, atleast a portion of the implant 10 is preferably compressible to allowmovement between the adjacent vertebrae. For example, the arms 14, 16,or a portion of the arms 14, 16, can be compressible by forming the arms14, 16 from a compressible material, embedding a compressible materialin the arms 14, 16, or by coupling a compressible material to a portionof the arms 14, 16. Suitable compressible materials include, by way ofnon-limiting example, biocompatible polymers and metals.

As previously indicated above, the implant 10 can also include a facetreplacement component 20 that is adapted to couple the disc replacementcomponent 12 to at least one adjacent vertebrae. While the facetreplacement component 20 can have a variety of configurations, and itcan be formed integrally with, coupled to, or be separate from the discreplacement component 12, in one exemplary embodiment, as shown in FIGS.1 A and 1 B, the facet replacement component 20 is in the form of firstand second lateral extensions 20 a, 20 b that extend from the discreplacement component 12. The lateral extensions 20 a, 20 b are coupledto opposed sides of the posterior portion 12 a of the disc replacementcomponent 12, and they can extend in either a superior direction, asshown, to couple to a superior vertebra, or they can extend in aninferior direction. A person skilled in the art will appreciate that theimplant 10 can include any number of lateral extensions extending in anydirection to facilitate attachment thereof to one or more vertebrae.

Each extension 20 a, 20 b can be coupled to the disc replacement member12 using a variety of techniques. In one exemplary embodiment, as shown,the extensions 20 a, 20 b are movably coupled to the disc replacementmember 12 to allow the extensions 20 a, 20 b to pivot with respect tothe disc replacement member 12 as the adjacent vertebrae move. A movableconnection can be formed using, for example, a ball and socket joint, apolyaxial joint, flexible extensions 20 a, 20 b, etc. Alternatively, theextensions 20 a, 20 b do not need to be connected to the discreplacement member 12, but rather they can merely be disposed withincorresponding recesses or sockets formed within the disc replacementmember 12, as shown in FIG. 1A which illustrates first and secondrecesses 18 a, 18 b formed in the posterior portion 12 a of the discreplacement member 12. While not necessary, an interference fit, acompression fit, or a mechanical interlock can optionally be used toretain the extensions 20 a, 20 b within the recesses 18 a, 18 b. Aperson skilled in the art will appreciate that a variety of techniquescan be used to provide a movable connection between the facetreplacement member 20 and the disc replacement member 12.

Each extension 20 a, 20 b can also have a variety of shapes and sizes,and the particular shape and size can vary depending on the intendedimplant location. In the illustrated embodiment, each extension 20 a, 20b has a substantially elongate cylindrical shape with rounded orspherical ends. One of the spherical ends on each extension 20 a, 20 ballows the extension 20 a, 20 b to pivot within the recesses 18 a, 18 bformed in the disc replacement member 12. The other end of eachextension 20 a, 20 b is preferably spherical to avoid potential damageto surrounding tissue. The size of each extension 20 a, 20 b can alsovary, but in an exemplary embodiment each extension 20 a, 20 bpreferably has a length that allows the extensions 20 a, 20 b to mate tothe pedicles or lamina of a vertebra.

The extensions 20 a, 20 b can also include features to facilitateattachment to a vertebra. While virtually any technique can be used,including both rigid and dynamic connections, in one exemplaryembodiment each extension 20 a, 20 b can be adapted to receive afastening element for mating the extensions 20 a, 20 b to a vertebra. Asshown in FIGS. 1A and 1B, each extension 20 a, 20 b includes a thru-bore22 a, 22 b formed therein with a bone screw 30 a, 30 b disposedtherethrough. The bone screws 30 a, 30 b can be polyaxially movablerelative to the thru-bores 22 a, 22 b of the extensions 20 a, 20 b, butin an exemplary embodiment the bone screws 30 a, 30 b are monoaxial torigidly connect the extensions 20 a, 20 b to a vertebra.

FIGS. 1C and 1D illustrate the implant 10 in use positioned betweenadjacent superior and inferior vertebrae V_(s), V_(i) (FIG. 1C onlyillustrates the inferior vertebra V_(i)). In an exemplary embodiment,the spinal column is accessed using a posterior surgical approach (whichcan include posterio-lateral approaches). Minimally invasive techniquescan be used to access the spinal column. Once the spinal column isaccessed, and prior to positioning the implant 10 between adjacentsuperior and inferior vertebrae V_(s), V_(i), standard surgicaltechniques can be used to remove the natural disc disposed between theadjacent vertebrae V_(s), V_(i), and also the facet joints extendingbetween the adjacent vertebrae V_(s), V_(i).

Once the disc and/or facets are prepared, the implant 10 can be guidedbetween the adjacent vertebrae V_(s), V_(i) by passing the spinal cordthrough the opening 17 b between the opposed arms 14, 16 of the discreplacement member 12, and into the opening 17 c in the posteriorportion 12 a of the disc replacement member 12. A spinal distractor orother devices known in the art can be used to distract the adjacentvertebrae V_(s), V_(i) and guide the disc replacement member 12therebetween. Alternatively, the disc replacement member 12 can have ashape that is adapted to distract the vertebrae V_(s), V_(i) as the discreplacement member 12 is inserted therebetween. Once implanted, asshown, the opposed arms 14, 16 are positioned between the adjacentvertebrae V_(s), V_(i), and the posterior portion 12 a of the implant ispositioned around the spinal cord and between the spinous processesS_(s), S_(i) of the adjacent vertebrae V_(s), V_(i). The adjacentvertebrae V_(s), V_(i) can articulate relative to the disc replacementmember 12, or alternatively the disc replacement member 12 can beadapted to engage the adjacent vertebrae V_(s), V_(i), as previouslydiscussed.

Once the disc replacement member 12 is properly positioned, theextension members 20 a, 20 b can be positioned within the recesses 18 a,18 b in the disc replacement member 12, or can otherwise be coupled tothe disc replacement member 12. A fastening element can be insertedthrough each extension member 20 a, 20 b and into the pedicles or laminaof the vertebra to couple the extension member 20 a, 20 b to thevertebra. As shown in FIG. 1D, first and second bone screws 30 a, 30 bare inserted through the extension members 20 a, 20 b and into thepedicles of the superior vertebra V_(s)(or the pedicles of an inferiorvertebra V_(i), if desired). While the extension members 20 a, 20 b arerigidly connected to the superior vertebra V_(s), the extension members20 a, 20 b can move with respect to the disc replacement member 12,thereby allowing the adjacent vertebrae V_(s), V_(i) to articulaterelative to one another.

FIGS. 2A and 2B illustrate another exemplary embodiment of a spinalimplant 100. The implant 100 is similar to implant 10 and generallyincludes a posterior portion 112 a that is adapted to be positionedaround a spinal cord and that can be coupled to at least one adjacentvertebrae, and an anterior portion 112 b that is adapted to bepositioned between adjacent vertebrae. In this embodiment, however, theimplant 100 does not have a unitary configuration, but rather it has amulti-piece construction. In particular, the implant 100 includes asuperior member 112 s, an inferior member 112 i, and at least onecentral member disposed therebetween and adapted to allow movement ofthe superior and inferior members 112 s, 112 i relative to one another.

The superior and inferior members 112 s, 112 i can vary in shape andsize, but in one exemplary embodiment the superior and inferior members112 s, 112 i are substantially U- or C-shaped such that that posteriorportion 112 a of the implant 100 is substantially curved orsemi-circular with a central opening 117 a formed therein to allow theimplant 100 to be positioned around the spinal cord using a posteriorsurgical approach, and the anterior portion 112 b of the implant 100includes opposed superior and inferior arms 114 s, 116 s, 114 i, 116 ithat can be positioned between adjacent vertebrae and that define anopening 117 b therebetween for allowing the spinal cord to passtherethrough. The superior and inferior members 112 s, 112 i can alsohave substantially planar configurations, or they can have a shape thatis adapted to match the contour of a vertebral endplate.

As indicated above, the implant 100 can also include at least onecentral member disposed between and adapted to allow movement of thesuperior and inferior members 112 s, 112 i relative to one another.While the implant 100 can include any number of central members, in theillustrated exemplary embodiment the implant 100 includes a four centralmembers 118 a, 118 b, 118 c, 118 d disposed between the superior andinferior members 112 s, 112 i. In particular, a first central member 118a is positioned between the first superior arm 114 s and the firstinferior arm 114 i, a second central member 118 b is positioned betweenthe second superior arm 114 s and the second inferior arm 114 i, andthird and fourth central members 118 c, 118 d are positioned on opposedlateral sides of the posterior portion 112 a of the implant 100 betweenthe superior and inferior members 112 s, 112 i.

The central members 118 a, 118 b, 118 c, 118 d can be coupled to thesuperior and inferior members 112 s, 112 i, or they can be removablydisposed between the superior and inferior members 112 s, 112 i. Forexample, in one embodiment the central members 118 a, 118 b, 118 c, 118d can be fixedly mated to one or both of the superior and inferiormembers 112 s, 112 i. The central members 118 a, 118 b, 118 c, 118 dcan, however, be adapted to pivot, rotate, or otherwise move relative tothe superior and inferior members 112 s, 112 i. In another embodiment,the central members 118 a, 118 b, 118 c, 11 8d can merely be disposedbetween the superior and inferior members 112 s, 112 i. The superior andinferior members 112 s, 112 i can optionally includes recesses formedtherein and adapted to seat the central members 118 a, 118 b, 118 c, 118d.

The shape and size of each central member 118 a, 118 b, 118 c, 118 d canalso vary, but in one exemplary embodiment the central members 118 a,118 b, 118 c, 118 d are adapted to allow movement between the superiorand inferior members 112 s, 112 i. This can be achieved by, for example,forming the central members 118 a, 118 b, 118 c, 118 d, or at least aportion of the central members 118 a, 118 b, 118 c, 118 d, from acompressible or resilient material. Alternatively, the central members118 a, 118 b, 118 c, 118 d can be inflatable to allow the superior andinferior members 112 s, 112 i to move relative to one another. In otherexemplary embodiments, the central members 118 a, 118 b, 118 c, 118 dcan have a shape that allows the superior and inferior members 112 s,112 i to articulate relative thereto. While the shape can vary, in theillustrated exemplary embodiment the first and second central members118 a, 118 b disposed between the arms 114 s, 114 i, 116 s, 116 i of theanterior portion 112 b of the implant 100 each have a generally oblongshape, and the third and fourth central members 118 c, 118 d disposedbetween the superior and inferior members 112 s, 112 i of the posteriorportion 112 a of the implant 100 each have a generally spherical shape.A person skilled in the art will appreciate that a variety of othertechniques can be used to movably couple the central members 118 a, 118b, 118 c, 118 d to the superior and inferior members 112 s, 112 i, or toallow movement between the superior and inferior members 112 s, 112 i.

FIGS. 2C and 2D illustrate the implant 100 positioned between adjacentsuperior and inferior vertebrae V_(S), V_(i)(FIG. 2C only illustratesthe inferior vertebra V_(i)). The implant 100 can be implanted using avariety of surgical techniques, and the particular technique can varydepending on the particular configuration of the implant 100. In oneexemplary embodiment, a posterior surgical approach is used, aspreviously described with respect to FIGS. 1C-1D. Once the vertebraeV_(S), V_(i) are prepared, the implant 100 can be inserted between theadjacent vertebrae V_(S), V_(i) with the central members 118 a, 118 b,118 c, 118 d pre-disposed between the superior and inferior members 112s, 112 i. Where the central members 118 a, 118 b, 118 c, 118 d areinflatable, the implant 100 is preferably inserted between the adjacentvertebrae V_(S), V_(i) with the central members 118 a, 118 b, 118 c, 118d in a deflated state. Once properly positioned between the adjacentvertebrae, an inflation medium, such as air or fluid, e.g., saline orgel, can be introduced into the central members 118 a, 118 b, 118 c, 118d to inflate the central members 118 a, 118 b, 118 c, 118 d. Theinflation medium can optionally be adapted to harden to form rigidcentral members 118 a, 118 b, 118 c, 118 d. While the central members118 a, 118 b, 118 c, 118 d are preferably pre-disposed between thesuperior and inferior members 112 s, 112 i when the implant 100 isinserted between the adjacent vertebrae V_(s), V_(i), a person skilledin the art will appreciate that techniques could be used to allow thecentral members 118 a, 118 b, 118 c, 118 d to be implanted prior toimplanting the superior and inferior members 112 s, 112 i.

While not shown, the implant 100 can also include features to facilitateengagement of the adjacent vertebrae at a location between the vertebraeand/or on the posterior surface of the adjacent vertebrae. As previouslydiscussed, suitable techniques for mating the implant 100 to adjacentvertebrae include, by way of non-limiting example, surface features,such as teeth, that engage the endplates of the vertebrae and/or aposterior portion of the vertebrae, surface coatings or materials thatallow bone growth into the implant 100 to occur, or other materials orfeatures that will engage the adjacent vertebrae. By way of non-limitingexample, in one exemplary embodiment the posterior portion 112 a and/orthe anterior portion 112 b of the implant 100 can include teeth formedon the superior and inferior members 112 s, 112 i and adapted to engagethe endplates of the adjacent vertebrae and/or a posterior portion ofthe vertebrae, such as the pedicles.

In another exemplary embodiment, the implant 100 can include one or moreextension members formed thereon or mated thereto and adapted to coupleto at least one vertebrae. The extensions members can be similar toextension members 20 a and 20 b shown in FIGS. 1A-1D, or they can have avariety of other configurations that allow the implant 100 to couple toat least one adjacent vertebrae. By way of non-limiting example, FIGS.3A and 3B illustrate one exemplary embodiment of an implant 100′ that issimilar to implant 100 but that has flange-like extension members 120a′, 120 b′, 120 c′, 120 d′ formed thereon for mating the superior andinferior members 112 s′, 112 i′ to adjacent vertebrae. In particular,the implant 100′ includes first and second extension members 120 a′, 120b′ formed on the superior member 112 s′ and extending in a superiordirection, and first and second extension members 120 c′, 120 d′ formedon the inferior member 112i′ and extending in an inferior direction. Theextension members 120 a′, 120 b′, 120 c′, 120 d′ can be formed at anylocation on the implant 100, but in an exemplary embodiment as shown theextension members 120 a′, 120 b′, 120 c′, 120 d′ are positioned onopposed lateral sides of the posterior portion 112 a′ of the implant100′ to allow the extension members 120 a′, 120 b′, 120 c′, 120 d′ to becoupled to the posterior surface of the adjacent superior and inferiorvertebrae V_(S), V_(i), as shown in FIG. 3B.

Each extension member 120 a′, 120 b′, 120 c′, 120 d′ can have a varietyof shapes and sizes. In the embodiment shown in FIGS. 3A and 3B, theextension members 120 a′, 120 b′, 120 c′, 120 d′ are integrally formedwith the superior and inferior members 112 s′, 112 i′, and thus theyhave a substantially planar configuration. Each extension member 120 a′,120 b′, 120 c′, 120 d′ also includes a thru-bore formed therein andadapted to receive a fastening element, such as a bone screw 130 a′, 130b′, 130 c′, 130 d′, for mating the extension members 120 a′, 120 b′, 120c′, 120 d′ to the vertebrae. A person skilled in the art will appreciatethat a variety of other mating techniques can be used.

FIG. 3B illustrates the implant 100′ in use, and as shown the first andsecond extension members 120 a′, 120 b′ are mated to a superior vertebraV_(s), and the third and fourth extension members 120 c′, 120 d′aremated to an adjacent inferior vertebrae V_(i). As a result, the superiormember 112 s′ is maintained in a substantially fixed position relativeto the superior vertebra V_(s), and the inferior member 112 i′ ismaintained in a substantially fixed position relative to the inferiorvertebra V_(i). The central members 118 a′, 118 b′, 118′, only three ofwhich are shown in FIGS. 3A and 3B, allow the vertebrae V_(s), V_(i) tomove relative to one another, thereby restoring normal function to thevertebrae V_(s), V_(i).

One skilled in the art will appreciate further features and advantagesof the invention based on the above-described embodiments. Accordingly,the invention is not to be limited by what has been particularly shownand described, except as indicated by the appended claims. Allpublications and references cited herein are expressly incorporatedherein by reference in their entirety.

1. A spinal implant, comprising: a substantially C-shaped member havingan anterior portion adapted to be positioned between adjacent vertebraeand a posterior portion adapted to be positioned around a spinal cordand to couple to a posterior surface of at least one adjacent vertebra.2. The implant of claim 1, wherein the anterior portion of the C-shapedmember has a shape adapted to allow articulation of adjacent vertebraerelative to one another.
 3. The implant of claim 1, wherein the C-shapedmember is of a unitary construction.
 4. The implant of claim 1, whereinthe posterior portion of the C-shaped member includes at least oneextension member extending therefrom and adapted to mate to a posteriorsurface of a vertebra.
 5. The implant of claim 4, wherein the at leastone extension member comprises first and second extension membersextending from opposed lateral sides of the posterior portion of theC-shaped member.
 6. The implant of claim 5, wherein the first and secondextension members extend in a superior direction from a superior surfaceof the posterior portion of the C-shaped member.
 7. The implant of claim4, wherein the at least one extension member comprises first and secondsuperior extension members extending in a superior direction fromopposed lateral sides of the posterior portion of the C-shaped member,and first and second inferior extension members extending in an inferiordirection from opposed lateral sides of the posterior portion of theC-shaped member.
 8. The implant of claim 7, wherein the first and secondsuperior extension members are movable relative to the first and secondinferior extension members.
 9. The implant of claim 4, wherein the atleast one extension member is movably coupled to the posterior portionof the C-shaped member.
 10. The implant of claim 4, wherein the at leastone extension member includes a thru-bore formed therein for receiving afastening element adapted to engage bone.
 11. The implant of claim 1,wherein the C-shaped member comprises a substantially C-shaped superiormember, a substantially C-shaped inferior member, and at least onecentral member disposed therebetween.
 12. The implant of claim 11,wherein the at least one central member comprises first and secondcentral members disposed between the anterior portion of the superiorand inferior members, and third and fourth central members disposedbetween the posterior portion of the superior and inferior members. 13.The implant of claim 11, wherein the at least one central member isadapted to articulate between the superior and inferior members.
 14. Theimplant of claim 11, wherein the at least one central member iscompressible to allow movement of the superior and inferior membersrelative to one another.
 15. A method for stabilizing adjacentvertebrae, comprising: positioning a posterior portion of an implantaround a spinal cord and between resected facets of adjacent vertebrae,the posterior portion of the implant being adapted to couple to at leastone of the adjacent vertebrae; positioning an anterior portion of theimplant between the adjacent vertebrae such that the adjacent vertebraeare adapted to move relative to one another; and coupling the posteriorportion of the implant to at least one of the adjacent vertebrae. 16.The method of claim 15, wherein the posterior portion of the implant iscoupled to opposed lateral sides of at least one of the adjacentvertebrae.
 17. A method for stabilizing adjacent vertebrae, comprising:accessing a patient's spinal column using a posterior surgical approach;removing a disc disposed between adjacent vertebrae; and posteriorlypositioning an implant around a spinal cord, between facet joints ofadjacent vertebrae, and between the adjacent vertebrae, the implanthaving a posterior portion that is adapted to couple to at least one ofthe adjacent vertebrae.
 18. The method of claim 17, further comprisingcoupling a posterior portion of the implant to at least one of theadjacent vertebrae.
 19. The method of claim 17, wherein the posteriorportion of the implant is coupled to at least one of the adjacentvertebrae by inserting at least one bone screw through at least oneextension formed on the posterior portion of the implant and into bone.20. The method of claim 17, wherein the implant is substantiallyC-shaped.